Swing shield for roto-slide sampler

ABSTRACT

AN AUTOMATICALLY OPENING SHIELD FOR A PARTICLE SAMPLER IN WHICH A PAIR OF SPRING LOADED SHIELDS PROTECT THE COLLECTOR PLATES FROM WIND IMPACTION. WHEN THE SAMPLER IS ENERGIZED THE SHIELDS OPEN UNDER INFLUENCE OF CENTRIFUGAL FORCE AND AIR PRESSURE.

Nov. 16, 1971 s, RAYNOR 3,620,078

SWING SHIELD FOR ROTOSLIDE SAMPLE-R Filed June 24, 1970 A mnnnnn 'INVENTOR.

GILBERT S. RAYNOR United States Patent US. Cl. 73-170 R 5 Claims ABSTRACT OF THE DISCLOSURE An automatically opening shield for a particle sampler in which a pair of spring loaded shields protect the collector plates from wind impaction. When the sampler is energized the shields open under influence of centrifugal force and air pressure.

SOURCE OF THE INVENTION This invention was made in the course of, or under a contract with the United States Atomic Energy Commission.

BACKGROUND OF THE INVENTION One of the devices in current use for sampling pollens and similar-sized particles in the atmosphere is a so-called roto-slide sampler which is rotated or spun at intervals to obtain impaction of the particles. This type of device, which is in widespread use, requires shielding when not collecting to protect the sampling surfaces from wind impaction during the periods of non-use.

One way which can be used to protect the sampling surfaces between periods of collection is to provide a removable hood. The use of a hood would require personal attention for removal and replacement and as a result, this arrangement would be impractical. Another possibility which has been tried for similar devices, is a hood which is pulled into protective position by a motor each time rotation of the slide holder ceases. More recently, centrifugal force operated shields have been developed where in one case the shields are drawn outward upon rotation to expose the fixed sampling surfaces and in another case, the shields are placed so that automatically retracting arms on which the sampling surfaces are mounted are swung into collection position when rotated.

These automatically operated shielding mechanisms however, suffer a variety of difiiculties including their greater expense, complexity, and lack of complete re liability.

SUMMARY OF THE INVENTION The difficulties and problems associated with the above mentioned automatically operated shielding devices for roto-slide samplers are substantially reduced or overcome by the present invention in 'which swing mounted shields are designed to uncover the sampling plates when the latter are rotated for the purposes of collection. The shields are drawn away from the collection slides by a combination of centrifugal force and air pressure against the tail sections of the shields. The resulting configuration is a simple shielding mechanism of great reliability and minimum expense.

It is thus a principal object of this invention to provide an automatically operated shield for sample collection plates of improved reliability and reduced expense.

Other objects and advantages of this invention will hereinafter become obvious from the following description of a preferred embodiment of this invention.

3,620,078 Patented Nov. 16, 1971 ice BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the figures, roto-slide sampler 10 consists of a platform 12 supporting a motor assembly 14 from which extends a motor drive shaft 16. The latter carries a sleeve 18 integral therewith to support a window type frame 22 supported by a rod 24. The latter is an extension of shaft 16. Frame 22, rod 24, sleeve 18, and shaft 16 all rotate as a single assembly when motor assembly 14 is energized.

Frame 22 supports a pair of collection plates 26 and 28 which are held in place by slip-on clamps 32 and 34, respectively. When frame 22 is rotating as illustrated in FIG. 2 in the direction shown by the arrow, particles in the air are impacted and collected on the leading edges of the collection plates which are exposed in the manner shown.

To protect the leading edges of collection plates 26 and 28 when frame 22 is not being rotated, a pair of shields 36 and 38 are pivotally mounted. Shield 36 has a pair of pivot pins 42a and 42b attached thereto inserted in appropriate openings in frame 22 while shield 38 has a pair of pivot pins, the upper one being 44a and the lower one (not visible) similarly mounted. Stop pins 46 and 48 on frame 22 limit the open movement of shields 36 and 38.

Each of shields 36 and 38 is identical in size and shape and mounted in similar fashion with respect to its collection plate. For example, shield 36 has a flat section 52 and a curled section 54, the latter being curved around to block off wind access to its collection plate 26 as shown in FIG. 1 when frame 22 is not rotating. Shield 36 is provided with a spring 56 connected between rod 24 and the tail edge of flat section 52 to bias it in that position. Shield 38 is provided 'With a similar spring 58. When frame 22 begins to rotate in the direction of the arrow in FIG. 2 under power provided by motor assembly 14, the combination of centrifugal force and the effect of wind resistance on the tail sections of shield 36 and 38 will rotate both of the latter against the biasing action of springs 56 and 58 to expose the leading edges of plates 26 and 28 to particulate impaction. Weights 63 and 64 on the tail edges of shields 36 and 38 are selected for and provide the exact amount of net centrifugal force required for this purpose.

In the operation of sampler 10, during standby conditions, shields 36 and 38 are pulled closed by their respective springs as shown in FIG. 1, and free rotation under the influence of wind is insufficient to cause the opening of shields 36 and 38. The selection of springs 56 and 58 as well as the size of weights 62 and 64 are such as to insure that they will not open until frame 22 is rotating at some predetermined rate. When motor assembly 14 is energized, shields 36 and 38 open and collection is begun, to end again after motor assembly 14 is deenergized and shields 36 and 38 retract into their standby positions.

It is thus seen that the shielding construction provided in accordance with this invention is automatically operable, reliable, simple and economic in construction.

What is claimed is:

1. In a device for sampling airborne particulate matter by impaction of said particulate on an exposed collection surface during rotation thereof, an improved 3 shielding arrangement for protecting said surface during periods of non-collection when said surface is not being rotated, comprising:

(a) rotatable frame means for carrying said exposed collection surface;

(b) shielding means pivotally mounted on said frame means; and,

(0) means for biasing said shielding means into a position protecting said collection surface from particulate impaction;

(d) said shielding means having means responsive to rotation of said frame means above a predetermined rate to cause said shielding means to rotate, overcoming said biasing means, and thereby exposing said collection surface to particulate impaction.

2. The sampling device of claim 1 in which said shield ing means includes an unbalanced weighted portion which under the effect of centrifugal force during rotation of said frame means tends to pivot said portion of said shielding means outwardly to overcome said biasing means.

3. The sampling device of claim 2 in which said biasing means is a spring connected between said weighted portion of said shielding means and a portion of said frame means closer to the axis of rotation of said frame means.

4 r 4. The sampling device of claim 2 in which said shielding means includes a curved section to enclose-saidcollection surface when said shielding means is in its protecting position, said curved section constituting the leading edge of said shielding means during rotation of said frame means.

5. The sampling device of claim 4 in which said weighted portion of said shielding means is exposed to wind resistance during rotation to contribute to the centrifugal force tending to pivot said shielding means away from protecting said collection surface.

References Cited UNITED STATES PATENTS 2,947,164 8/1960 Orr, Jr. 73-28 2,973,642 3/1961 Grinnell et a]. 73-28 X 3,462,995 8/1969 Weiss 73-421 LOUIS R. PRINCE, Primary Examiner D. M. YASICH, Assistant Examiner US. Cl. X.R. 

